A |
Table 13. RedundancyOptions
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Option | Key | PLC | Scan | Data | I/O System | Selection | Redund. | Redund. | SelectionGuide |
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| Sync | Sync |
| Method | Bus | I/O |
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| 1A | no | Application | Hot | yes - 2 | no | Higher Density Analog Inputs | ||
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| Logic [ | (I/OScanner) | Standby |
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Hot Standby | 1B | no | Application | Hot | yes - 2 | no | MorecompetitiveI/O | ||
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| Logic [ | (GCM+) | Standby |
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Application | 1C | no | Application | GeniusI/O | Hot | yes - 2 | no | Highly distributable with diagnos- | |
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| Logic [ |
| Standby |
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| tics. Thermocouple. RTD |
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| 1D | no | Application | Hot | yes - 2 | no | Least expensive. Limited to | ||
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| Logic [ | (GCM+) | Standby |
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| 512 Inputs, 512 Outputs |
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Hot Standby | 2 | yes | Operating | Hot | yes - 2 | no | Redundant Bus Applications. | ||
Product plus |
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| System | (GCM+) | Standby |
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| MorecompetitiveI/O. |
ApplicationLogic |
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| 3A | yes | Operating | Hot | no | no | Higher Density Analog Inputs | ||
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| System | (I/OScanner) | Standby |
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Hot Standby Product | 3B | yes | Operating | Hot | no | no | MorecompetitiveI/O. | ||
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| System | (GCM+) | Standby |
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| 3C | yes | Operating | GeniusI/O | Hot | no | no | Highly Distributable with diagnos- | |
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| System |
| Standby |
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| tics. Thermocouple. RTD. |
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ESD Duplex | 4 | no | no | GeniusI/O | Duplex | yes - 2 | yes | For | |
ApplicationLogic |
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ESD Duplex | 5A | no | no | GeniusI/O | GMR | yes - 2 | yes | For Fail±Safe or fault tolerant ESD | |
GMR Product |
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| applications. |
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ESD Triplex | 5B | no | no | GeniusI/O | GMR | yes - 3 | yes | For fault tolerant ESD applications. | |
GMR Product |
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[See list of restrictions below.
Explanation of terms used in the above Table of Redundancy Options.
Hot Standby Redundancy | Two CPUs are connected to one or more I/O. One CPU is active; the other is in standby. If the active |
| unit fails, the standby unit takes control of the process (Hot Standby Redundancy is sometimes |
| known as Hot Backup Redundancy). |
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Scan Synchronization | Scan mechanisms may be synchronized to keep active and standby units in lockstep to minimize |
| ºbumpsº or upsets to the process when switching from active to standby unit. |
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Data Synchronization | Keeps standby unit refreshed with the current state of the active unit to minimize ºbumpsº or upsets |
| to the process when switching from active to standby unit. |
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Emergency Shutdown System (ESD) | Two or three unsynchronized CPUs solve logic asynchronously based on common inputs. Output |
| state is voted on by the output devices. The inputs and outputs are normally energized and do not |
| change state. DUPLEX ESD is Failsafe while TRIPLEX ESD is fault tolerant. |
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Has many restrictions (see the list of restrictions on page 13). | |
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ProductSolutions | Has functions built into the operating system that make the system easier to engineer and more |
| robust. Product solutions are preferable to application solutions from a support perspective. |
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Output Selection Method | Refers to the algorithm in the I/O device, such as Hot Standby, Duplex, or No Redundancy Modes. |
| These modes may refer to existing Genius I/O terminology. GMR (Genius Modular Redundancy) |
| mode is a voting algorithm available in Genius I/O DC blocks. |
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FailSafe | An ESD system will fail such that the process under supervision will be shutdown. |
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Fault Tolerant | In an ESD system any single failure will not disrupt the process under supervision. |
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Appendix A Redundancy Alternatives | 87 |
